LBNL, Berkeley, California
The recent availability of ultrashort (femtosecond) electron bunches is accompanied by the necessity for ultrafast bunch characterization, preferably in a single-shot manner. The duration of the bunch, its precise charge profile, and/or its arrival time, are parameters relevant to accelerator performance and experimental applications. The electro-optic (EO) technique has proven ideal as a single-shot femtosecond bunch diagnostic. The technique is based on the polarization modulation of a laser pulse by either the self-fields of the electron bunch, or by the coherent radiation emission of the bunch. The technique is limited in time resolution only by the laser pulse length (<10's of fs). We will present an overview of the several variations of existing EO configurations (analysis in spatial, temporal, or frequency domain), each with its own set of advantages and limitations. Both modeled and experimental results will be presented. Emphasis is put on results on electron bunches from the 10-TW-laser-based Laser Wakefield Accelerator of the LOASIS group at LBNL. These bunches were found to have a duration of 45 fs. Future improvements on the EO technique will be discussed.
Fermilab, Batavia
We present preliminary measurements of the electron bunch lengths at the Fermilab A0 Photoinjector using a Martin-Puplett interferometer on loan from DESY. The photoinjector provides a relatively wide range of bunch lengths through laser pulse width adjustment and compression of the beam using a magnetic chicane. We present comparisons of data with simulations that account for diffraction distortions in the signal and discuss future plans for improving the measurement.